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Nephrogenic diabetes insipidus — SCE Endocrinology MCQ

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HardPituitaryNephrogenic diabetes insipidusSCE Endocrinology

During unstimulated adrenal-vein sampling, cortisol is 750 nmol/L on the right, 900 nmol/L on the left and 300 nmol/L in the IVC. Aldosterone is 3,000 pmol/L on the right and 900 pmol/L on the left. What do these data show?

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Correct answer: C — Both veins are selective and the lateralization index is 4.0 to the right

C is correct. Selectivity indices are right 750/300 = 2.5 and left 900/300 = 3.0, consistent with successful unstimulated sampling using a threshold around 2. Corrected aldosterone-to-cortisol ratios are right 3000/750 = 4 and left 900/900 = 1; the lateralization index is therefore 4.0 toward the right. Absolute aldosterone alone cannot determine laterality, and an arbitrary cortisol concentration does not replace the selectivity ratio.

Reference: Endocrine Society primary aldosteronism guideline: https://academic.oup.com/jcem/article/110/9/2453/8196671